1. Field of the Invention
The present invention relates to a preview function which makes it possible to confirm an image corresponding to image data by a data generating apparatus, such as a computer, before an image made from the image data is actually outputted from an output apparatus, such as a printer, connected with the data generating apparatus.
2. Description of the Related Art
In a case that image data is generated by a computer and an image made from the image data is printed out by a printer connected with the computer, an image corresponding to the image data is previewed in order to confirm the image before the image is actually printed out.
Namely, the image data generated by the computer is outputted from the computer to the printer at first. The image data is described by using a page description language, for example. Next, in the printer, the image data is converted into bitmap data. Further, the bitmap data is supplied to a print engine, and an image made from the bitmap data is printed out by the print engine.
At this time, there is a case that an actual image printed out by the printer is different from an image which a user has desired. In order to prevent such an incorrect image from printing out by the printer, it is necessary to confirm the image corresponding to image data by the computer before the image is actually printed out by the printer. For such a reason, the computer has a preview function which makes it possible to confirm the image corresponding to the image data by a display. In the computer having the preview function, the image to be previewed on the display, i.e., the preview image is made by using font data, etc. stored in the computer itself.
Further, trimming, tiling, color correction and a change of size are carried out on the basis of the preview image displayed on the display of the computer.
Trimming is a process to delete a peripheral portion of the image before printing. When the trimming is carried out, a user decides a peripheral portion on the basis of the preview image displayed on the display of the computer.
Tiling is a process to divide the image into plural parts when the size of the image exceeds the size of the printing paper. When the tiling is carried out, a user decides a position of a dividing line on the basis of the preview image displayed on the display of the computer.
Color correction is a process to correct colors of the image in order to equalize colors of the image to a desired colors. When the color correction is carried out, a user decides colors on the basis of the preview image displayed on the display of the computer.
A change of size is carried out in a case that it is necessary to change a size of the image at the time of printing. At this time, a user decides a size of the image on the basis of the preview image displayed on the display of the computer.
Here, in case that one printer is shared with a plurality of computers by using a network or the like, various types of computers are connected with one printer through the network. If font data stored in one of the computers connected with the printer is different from that stored in the printer, and if a program (to be used for converting image data in order to produce an image) installed in one of the computers connected with the printer is different from that installed in the printer, it is not possible to display a preview image equal or similar to an actual image printed by the printer. If the font data equal to that stored in the printer is installed in all of the computers connected with the printer, it may be possible to display a preview image equal or similar to an actual printed image at each computer. But, actually, this is difficult and troublesome.
Further, if a preview image is different from an actual image printed by a printer, trimming, tiling, color correction and a change of size cannot be correctly carried out on the basis of the preview image displayed on a display of each computer.
In order to display a preview image equal or similar to an actual image printed by a printer, it is proposed that bitmap data converted by the printer is used for the preview. Namely, at first, image data described by the page description language is sent to the printer from each computer. Next, the sent image data is converted into binary bitmap data having low graduation in the printer. Thereafter, the bitmap data is thinned out in the printer in order to match the bitmap data to a resolution of the display of each computer. Further, the thinned out bitmap data is sent to each computer from the printer as preview data. Thus, an preview image made from the preview data is displayed on the display of each computer.
However, if the bitmap data is simply thinned out, the preview image displayed on the display is unclear or broken due to a quantization difference between each computer and the printer. For instance, lines forming the preview image are partially disappeared, an edge of the preview image becomes unclear, or an irregular color, such as moire, is occurred in the preview image. These facts are especially serious problem in color printing.
Namely, in a printing system used in a laser printer, an inkjet printer or the like, an image printed by such a printer is constructed by a plurality of dots. The dot is a smallest part of a printed image. An image is formed by an on/off of each dot. In this case, bitmap data corresponds to each dot of an image. Namely, the bitmap data is data in which an on/off of each dot is recorded. Thus, if the bitmap data is simply thinned out, the bitmap data is partially lost and lines forming the preview image are partially disappeared.
Further, in such a printing system, when an image having intermediate graduation is printed or displayed, a half tone screening technique or the like is used. In the half tone screening technique, a picture element is constructed by a plurality of dots. The concentration of a picture element is changed with the number of the dots being an on condition. In case that the half tone screening technique is used, bitmap data corresponds to each dot constructing each picture element. Therefore, if bitmap data is simply thinned out, the contours of the preview image is unclear.
Furthermore, an irregular color occurred in the preview image can be attributed to interference between a sampling frequency using quantization when an original image is converted to bitmap data and a sampling frequency using quantization when the bitmap data is further converted to the preview data. Concretely, some stripes formed by different concentrations are appeared in the preview image. This phenomenon is called moire.
On the other hand, in case that one printer is shared with a plurality of computers, each computer may have a display having a different resolution and the different number of colors. However, the conventional printer generates only one type of preview data. Namely, the conventional printer cannot generate preview data suitable for different resolution and different color (the number of color). As a result, it is impossible to display a correct preview image on the display of every computer connected with the printer.